| Chagos Islands - Other Islands, Atolls & Reefs |
| Benares Shoals |
Benares Shoals (or Benares Shoal) is a submerged coral reef, an isolated patch located at 5°15′S 071°40′W / -5.25, -71.667, -71.667, just 6 km WNW of Île Pierre, the closest island of Peros Banhos atoll in the northern Chagos Archipelago. It measures about 3 km east-west, with a width of about 700 meters, and an area of 2 km². The least depth at the western end is 4.5 meters.
The Benares Shoals were first surveyed in 1837 by Commander Robert Moresby of the Indian Navy on the HMS Benares. Moresby's survey produced the first detailed map of this submerged reef, which was subsequently named after his ship. |
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| Blenheim Reef |
| Blenheim Reef, part of the Chagos Archipelago, contains the coral atoll of Baxio Predassa in its Southeastern rim, plus another completely submerged atoll. The reef is located in the northeastern part of the Chagos Archipelago, at 5°12′S 072°28′E / -5.2, 72.467Coordinates: 5°12′S 072°28′E / -5.2, 72.467. It measures almost eleven kilometres (North–South) by more than four kilometres (East–West), with a total area of 36.8 square kilometres, including the lagoon of 8.5 km² (the difference being accounted for by the reef flat, for the most part). Only on the Eastern side, there are a few sand cays above the water. The largest of them is East Island, which is not quite 200 meters long and 70 meters wide. The other islands in the group are North, Middle and South. Only a few grasses grow on the island. The lagoon is up to 18 metres deep and encumbered with rock. The fringing coral reef has a wide passage in the Southwest. The closest land is Takamaka Island in the Salomon Islands Atoll, about 20 kilometres to the southwest. |
| History |
The atoll is thought to have been discovered around 1570 by Portuguese sailors, which is why it is also known under its Portuguese name Baixo Predassa. The present name comes from the ship Blenheim of the East Indian Trading Company, which was lost in 1799 to the reef.
From 1845 to 1860, guano and phosphate were mined. This venture was then given up due to inadequate transport facilities. Around 1880, the Indian Ocean Fruit Company attempted to plant palm trees on the island, but all seedlings were washed into the sea during a storm. On June 29, 1975, the atoll was incorporated into the Chagos Archipelago and claimed by Mauritius. Before that day, it was not claimed by any nation.
In total, there have been 57 ship wrecks around Blenheim Reef, with an estimated 200 lost lives. |
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| Cauvin Bank |
| Cauvin Bank is a wholly submerged atoll structure in the Southern Part Chagos Archipelago at 6°46′S 172°22′E / -6.767, 172.367, just about 7 km South of the Southeastern corner of the rim of the Great Chagos Bank. It is roughly circular in shape, with a diameter of 4 km, and an area of about 12 km². There are least depths between 9 and 11 meters in the Northern part of the reef. The closest land is the Northernmost part of Diego Garcia atoll, Middle Island, 45 km to the South. |
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| Centurion Bank |
| Centurion Bank is a wholly submerged atoll structure in the Southwest of the Chagos Archipelago. It is the southermost feature of the archipelago. It is about almost 10 km long northwest-southeast, and more than 3 km wide. The reef area is about 25 km². |
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| Colvocoresses Reef |
| Colvocoresses Reef is a wholly submerged atoll structure in the Northeast of the Chagos Archipelago, 15 km East of Speakers Bank and 28 km Northeast of Blenheim Reef. It is named after Dr. Alden Partridge Colvocoresses who developed in 1973 - 1979 the Space-oblique Mercator projection with John Parr Snyder and John L. Junkins. The least charted depth is 9 meters deep above the reef. Breakers are visible only during heavy seas. The reef measures 8 km north-south, and is 1 to 2 km wide , with a total area of about 10 km². |
| Colvocoresses Reef is unique in that it is was discovered by use of images taken by the National Aeronautics and Space Administration's (NASA) Landsat Satellite. The Landsat images the earth with several spectral bands. Each band provides a black and white image that is taken through a spectral filter. It has two non-thermal infrared bands for sensing plant vigor. These bands have very limited water penetration. Landsat also has two visible wavelength bands: red and green. The green band has been proven to see through clear ocean waters to depths of about 30-40 meters. |
| In 1975, the Defense Mapping Agency's Hydrographic Center, subsequently incorporated into the National Geospatial-Intelligence Agency (NGA), requested NASA to collect Landsat images over the Chagos Archipelago. The images revealed the previously uncharted Colvocoresses Reef as well as errors in positioning of numerous other reefs in the Archipelago. Some were out of position by as much as 18 kilometers. By the summer of 1976 a new chart of the Chagos Archipelago was printed showing the corrected positions of the banks and shoals as well as Colvocoresses Reef. This was the first nautical chart known to have been completely revised using the Landsat imagery. |
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| Eagle Islands |
| Eagle Islands is a group of two islands in the Chagos Archipelago, Eagle Island (Île Aigle) and Sea Cow Island (Île Vache Marine). They are located on the central-western rim of the Great Chagos Bank, which is the world's largest coral atoll structure. With a land area of 2.45 km², Île Aigle is the largest single island of the Great Chagos Bank, and after Diego Garcia the second largest of the Chagos Archipelago. |
| There was once a coconut plantation in Ile Aigle, as well as a small settlement of Chagossian plantation workers. But at the time of Commander Robert Moresby's survery of the Chagos, in 1838, this island was populated only occasionally. Not long after the settlement of the Chagos group by the French planters at the end of the 1700s, the tendency was to concentrate the workers on only a few islands from which the plantations were run, like Ile Boddam in the Salomon Atoll. |
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| Ganges Bank |
| Ganges Bank is a wholly submerged atoll structure in the Southwest of the Chagos Archipelago. It is about 7 by 5 km in size, yielding an area of about 30 km². |
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| Great Chagos Bank |
| The Great Chagos Bank, in the Chagos Archipelago, about 500 km South of the Maldives, is the largest atoll structure in the world, with a total area of 12 642 km². There are seven or eight individual islands on the rim of the atoll, one in the North (Nelson's Island) and the others on the Eastern rim. The total land area of the islands is about 4.5 km². |
| The individual islands, starting in the South clockwise, are: |
| Danger Island (slightly more than 2 km long from North to South, up 1 km wide, land area 0.66 km², vegetated with palm trees up to 12 m high, Strict Nature Reserve since 1998) |
Eagle Islands
Île Aigle (Eagle Island, vegetated with high coconut trees, land area 2.45 km²
Sea Cow Island (Île Vache Marines), vegetated with trees, land area 0.18 km², Strict Nature Reserve since 1998) |
| Three Brothers (Trois Fréres) and Resurgent Islands (vegetated with high coconut trees, land area 0.4 km², Strict Nature Reserve since 1998) |
| Île du Sud (South Island, largest of the group), 0.23 km² |
| Île du Mileu (Middle Island), 0.08 km² |
| unnamed rocky islet |
| Île du Nord (North Island), 0.06 km² |
| Nelsons Island (2 km long from East to West, up to 1 km wide, land area 0.81 km², 3 m high, bushy vegetation, Strict Nature Reserve since 1998) |
| Cartography of the Submerged Reefs |
| The Great Chagos bank was surveyed for the first time by Commander Robert Moresby of the Indian Navy in 1837. Although the charts of "normal" atolls like Peros Banhos and Diego Garcia were relatively accurate, the cartography of the vast sunken reefs forming the Great Chagos Bank proved quite a challenge. The real shape of these sunken reefs was known only when satellite imagery became available in the latter part of the 20th century. |
| Moresby's original hydrographic drawings were somewhat at variance with the true shape of the submerged reef, especially in areas where there were no emerging islands close by, like in the South east of the bank. The outlines of the first hydrographic surveys are still marked in present-day navigational maps of the Chagos with a dotted line and the legend "existence doubtful". |
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| Nelson Island |
| Nelson Island is the northernmost and the easternmost island of the Great Chagos Bank, which is the world's largest coral atoll structure, located in the Chagos Archipelago in the Indian Ocean. The nearest neighbor is Île Boddam in the Salomon Islands. |
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| Owen Bank |
| Owen Bank is a wholly submerged atoll structure in the Chagos Archipelago. The reported location is 06°47'S, 070°14'E to 06°48'S, 070°15'E, thus the bank is the westernmost feature of the Chagos Archipelago. The closest islands are Danger Island on the Great Chagos Bank, and Île Sipaille in the Egmont Islands atoll, both of which are about 120 km East-North-East of Owen Bank. |
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| Pitt Bank |
Pitt Bank is a wholly submerged atoll structure in the Southwest of the Chagos Archipelago. It is almost 56 km long Northwest to Southeast, with a width between 20 and 30 km. It stretches from 06°48'S to 07°16'S and 071°06'E to 071°36'E. The total size is 1317 km 2, making it the second largest atoll structure in the Chagos Archipelago, after the Great Chagos Bank, and before Speakers Bank. The closest land is Île Lubine of Egmont Islands atoll, 22 km Northeast of the Northern end of Pitt Bank. The least depth is 7 meters at the Southeastern Rim, and the deepest areas of the former lagoon reach 44 meters.
This submerged atoll was named after William Pitt the Younger, who was a British Prime Minister in 1783–1801 and 1804–1806. A buoy, marked by a radar reflector, is moored on the NW side of the bank. |
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| Victory Bank |
| Victory Bank is a wholly submerged atoll structure in the Northern Chagos Archipelago at 05°33'S, 0172°14'E, about midway between Danger Island on the Northern rim of the Great Chagos Bank, which is 16 km Southeast of it, and Île Boddam, of the Salomon Islands, which is 17 km to the North. It is roughly elliptical in shape, with a size of 6 km East-West and 4 km North-South, and an area of about 19 km². It rises steeply from great depths. The lagoon is up to 33 meters deep, while the depth along much of the rim is only 5.5 meters. |
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| Wight Bank |
| Wight Bank is a small, wholly submerged atoll structure in the Southwest of the Chagos Archipelago, about 1820 km SWS of the southern tip of India. The location is 7°25′S 71°31′E / -7.417, 71.517Coordinates: 7°25′S 71°31′E / -7.417, 71.517. It was first reported in 1886. It is less than 2 km in diameter. The total area is about 3 km 2. The closest piece of land is Île Sudest of Egmont Islands atoll, 80 km NWN. Diego Garcia is 94 km to the East. The least charted depth is 8.5 meters. |
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